This video really encapsulate the essence of depression. It takes four minutes and I vividly recommend watching it!

The allegory of the black dog is said to have come from Winston Churchill who, despite the key historical accomplishments he led in his life, was affected by depression, bipolar disorder, suicidal thoughts. He is not the only public figure in fact who has experienced or led a successful life with a mental health condition: Abraham Lincoln, Beethoven, Munch, Dickens, Jim Carey, James Franco, the late Robin Williams. I also listened to a podcast of @movember (Available on soundcloud) where Jason Fox from SAS talks about how he’s dealt with PTSD.
Take example from some of these men, take the steps necessary to tame your black dog, seek professional help, learn to live with it and make it smaller, outrun him, and above all, find some close friends that you can open up to and introduce him to.